Resumen

Flavonoids are polyphenolic compounds widely distributed in the plant kingdom, mainly in dietary fruits, vegetables and derived products such as wine and chocolate, and quercetin is the most abundant and the best studied one. Flavonoids have been proposed to exert beneficial effects in the prevention of a large number of diseases, including cancer, cardiovascular disease, and neurodegenerative disorders. Theflavonoid class includes several thousand compounds as found in nature, including several subclasses such as flavonols, flavones, flavanones, flavanols, anthocyanidins,isoflavones, dihydroflavonols and chalcones. They are regularly ingested in the diet as complex mixtures of different flavonoid compounds together with other activesubstances. Flavonols are present, usually as diverse glycosides, in considerable amounts in our normal diet. Although flavonols can be found virtually in all vegetablesand fruits, the richest sources include onions, apples, cider, grapes, wine and tea. After oral ingestion, flavonoids are subject to chemical modification within thegastrointestinal tract by the enzymes of the host and microbiota and further metabolized after absorption in the intestinal wall, the liver and peripheral tissues.In the introduction, the state of the art of cardiovascular effects of flavonoids is reviewed as well as their pharmacokinetics. Even when not all epidemiological studiesreported an inverse association between dietary flavonoid consumption and mortality from cardiovascular diseases, a large body of evidence supports the hypothesis thatflavonoids exert protective cardiovascular effects. Flavonols, and specially quercetin, in addition to its anti-oxidant effect, can modulate (mostly inhibit) the activity of an impressive number of enzymes. Thus, it can be predicted that a huge number of biochemical signalling pathways and, therefore, physiological and pathologicalprocesses, can be affected by thisfl avonol. It can potentially interact with many of the molecular targets known to be involved in the pathophysiology of ischemic heart disease and stroke. Thus, it may act by multiple mechanisms operating both in the long term prevention and in the acute phase of cardiovascular events. To summarize, there is solid evidence that, in vitro, quercetin and relatedfl avonols exert: (1) endothelium -independent vasodilator effects, (2) protective effect on nitric oxide and endothelial function under conditions of oxidative stress, (3) platelet antiaggregant effects, (4)inhibition of LDL oxidation, (5) reduction of adhesion molecules and other...